Symmetric Signcryption and E2EE Group Messaging in Keybase

ePrint Report: Symmetric Signcryption and E2EE Group Messaging in Keybase

Joseph Jaeger, Akshaya Kumar, Igors Stepanovs

We introduce a new cryptographic primitive called symmetric signcryption, which differs from traditional signcryption because the sender and recipient share a secret key. We prove that a natural composition of symmetric encryption and signatures achieves strong notions of security against attackers that can learn and control many keys. We then identify that the core encryption algorithm of the Keybase encrypted messaging protocol can be …

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